/*
 * The MIT License (MIT)
 * Copyright © 2019 <sky>
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the “Software”), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
package com.sky.framework.common;

import lombok.extern.slf4j.Slf4j;
import org.apache.commons.codec.binary.Base32;
import org.apache.commons.codec.binary.Base64;

import javax.crypto.Mac;
import javax.crypto.spec.SecretKeySpec;
import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;

/**
 * GoogleAuthenticator
 * 双重验证
 * 使用方式:
 * 根据账号和域名生成
 *
 * @author
 */
@Slf4j
public class GoogleAuthenticator {

    /**
     * taken from Google pam docs - we probably don't need to mess with these
     */
    private static final int SECRET_SIZE = 10;

    /**
     * 种子， 有点像加盐
     */
    private static final String SEED = "g8GjEvTbW5oVSV7avLBdwIHqGlUYNzKFI7izOF8GwLDVKs2m0QN7vxRs2im5MDaNCWGmcD2rvcZx";

    /**
     * 随机数字算法
     */
    private static final String RANDOM_NUMBER_ALGORITHM = "SHA1PRNG";

    /**
     * default 3 - max 17 (from google docs)最多可偏移的时间
     * 允许客户端的验证码变换 [window_size] 次范围内可验证成功
     */
    private int window_size = 3;

    private void setWindowSize(int s) {
        if (s >= 1 && s <= 17) {
            window_size = s;
        }
    }

    /**
     * 生成密钥
     */
    public static String generateSecretKey() {
        try {
            SecureRandom sr = SecureRandom.getInstance(RANDOM_NUMBER_ALGORITHM);
            sr.setSeed(Base64.decodeBase64(SEED));
            byte[] buffer = sr.generateSeed(SECRET_SIZE);
            Base32 codec = new Base32();
            byte[] bEncodedKey = codec.encode(buffer);
            return new String(bEncodedKey);
        } catch (NoSuchAlgorithmException e) {
            LogUtils.error(log, "生成密钥异常:{}", e);
        }
        return null;
    }


    /**
     * 获取QR条形码URL, 用这个生成二维码，给Google验证器扫码
     */
    public static String getQRBarcodeURL(String user, String host, String secret) {
        String format = "https://www.google.cn/chart?chs=200x200&chld=M%%7C0&cht=qr&chl=otpauth://totp/%s@%s%%3Fsecret%%3D%s";
        return String.format(format, user, host, secret);
    }

    /**
     * 验证码动态验证码
     *
     * @param secret   密码，上面方法生成的
     * @param code     动态验证码
     * @param timeMsec 毫秒时间搓 System.currentTimeMillis()
     */
    public boolean checkCode(String secret, String code, long timeMsec) {
        Base32 codec = new Base32();
        byte[] decodedKey = codec.decode(secret);
        // convert unix msec time into a 30 second "window"
        // this is per the TOTP spec (see the RFC for details)
        long t = (timeMsec / 1000L) / 30L;
        // Window is used to check codes generated in the near past.
        // You can use this value to tune how far you're willing to go.
        for (int i = -window_size; i <= window_size; ++i) {
            String hash;
            try {
                hash = verifyCode(decodedKey, t + i);
            } catch (Exception e) {
                // Yes, this is bad form - but
                // the exceptions thrown would be rare and a static configuration problem
                LogUtils.error(log, ":{}", e);
                throw new RuntimeException(e.getMessage());
                //return false;
            }
            if (hash.equals(code)) {
                return true;
            }
        }
        // The validation code is invalid.
        return false;
    }


    private static String verifyCode(byte[] key, long t) throws NoSuchAlgorithmException, InvalidKeyException {
        byte[] data = new byte[8];
        long value = t;
        for (int i = 8; i-- > 0; value >>>= 8) {
            data[i] = (byte) value;
        }
        SecretKeySpec signKey = new SecretKeySpec(key, "HmacSHA1");
        Mac mac = Mac.getInstance("HmacSHA1");
        mac.init(signKey);
        byte[] hash = mac.doFinal(data);
        int offset = hash[20 - 1] & 0xF;
        // We're using a long because Java hasn't got unsigned int.
        long truncatedHash = 0;
        for (int i = 0; i < 4; ++i) {
            truncatedHash <<= 8;
            // We are dealing with signed bytes:
            // we just keep the first byte.
            truncatedHash |= (hash[offset + i] & 0xFF);
        }
        truncatedHash &= 0x7FFFFFFF;
        truncatedHash %= 1000000;
        return String.valueOf(truncatedHash);
    }
}
